Phytophthora oak decline; Root rot - Phytophthora quercina
EEffective: August 18, 2010 - December 31, 2019
Taxonomic Position:
Peronosporales : Pythiaceae
Pest Type:
Fungi
Pest Code (NAPIS):
FGANPYC
This pest is a member of the following lists:
These Approved Methods are appropriate for:
2019, 2018, 2017, 2016, 2015
Pest is vectored by:
No known vector.
Survey
Approved Method(s):
Method |
Instructions |
NAPIS Survey Method |
Water Sample |
In situ water sampling with rhododendron leaf baits (preferred method). See details below. |
3014 - General Water Sample
|
Visual |
Collect soil or root sample from symptomatic trees. |
3031 - General Visual Observation
|
Survey Instruction Details:
Use rhododendron leaves as bait by cutting the leaves in a herringbone pattern. Place 3-4 cut leaves into a mesh bag. Place the mesh bag into the water source for a minimum of 48 hours to 1 week (preferable).
Signs:
No specific signs are present.
Symptoms:
Twig abscission, epicormic shoots, crown thinning, branch and crown dieback, reduced growth, yellowing leaves.
Key Diagnostics
ID/Diagnostic: Multiple
Serological: An ELISA of dipstick test is available for Phytophthora at the genus level for primary screening. A positive does not indicate P. quercina.
ID must be confirmed by other methods.
Morphological:
1.Baiting technique (soil):
a.Submerge a rhododendron leaf, oak leaflet in soil sample. Cover with water. Remove baits after 48 hrs. Examine for lesions after 7 days.
b.Species are identified morphologically (Jung et al., 1999).
2.Direct Isolation (bark/roots):
a.Place pieces of tissue on semi-selective media.
b.Species are identified morphologically (Jung et al., 1999).
Mistaken Identities:
Symptoms of P. quercina are not characteristic as they are common for other forest Phytophthora species.
In Progress / Literature-based Diagnostics:
Molecular: PCR has been used to detect P. quercina in leaves.
Nested PCR has been used to detect P. quercina in soil and water samples (Schubert et al., 1999; Nechwatal et al., 2001).
Real-time PCR: method has been developed that uses two universal primers and a probe to monitor the quality of DNA extracted from environmental samples followed by a multiplex real-time PCR to detect P. quercina, P. ramorum, P. kernoviae, and P. citricola from symptomatic leaves (Schena et al., 2006).
Schena et al. (2008) developed a PCR-based molecular tool box that could identify 15 Phytophthora species that damage forests and trees.
Single-strand conformation polymorphism (SSCP) analysis of PCR-amplified ribosomal DNA internal transcribed region I has now been used to identify and provide a molecular fingerprints for 59 Phytophthora species, including P. quercina (Gallegly and Hong, 2008).
Notes:
P. quercina was reported from Missouri; however, the identification was never validated molecularly or verified by APHIS (Schwingle et al., 2007).